试论有机质与后生砂岩型铀矿成矿作用--以吐哈盆地十红滩地区为例

在很多砂岩型铀矿床中 ,可以发现铀与有机质之间有着密切关系 ,这种关系可以是数理统计意义上的、空间上的或化学的。本文以吐哈盆地十红滩地区砂岩型铀矿为研究对象 ,对有机质在后生砂岩型铀矿成矿中的作用进行了探索。研究区砂岩型铀矿含矿岩系中的有机质属腐殖型 ,其原始母质为陆生高等植物 ,有机质成熟度很低 ,处于热演化作用的褐煤阶段。铀与有机碳的相关性分析和分离实验表明铀成矿富集与有机质关系密切 ,在铀矿石中铀与有机质主要以腐殖酸吸附或腐殖酸盐形式存在。笔者认为 ,在氧化带有机质被氧化破坏 ,形成可溶性的铀腐殖酸络合物淋滤进入地下水 ,在过渡带以腐殖酸盐的形式沉淀下来 ,并造成过渡带矿石中有机碳含量的增高

DISCUSSION ON RELATIONSHIP BETWEEN ORGANIC MATTER AND METALLOGENESIS OF EPIGENETIC SANDSTONE-TYPE URANIUM DEPOSITS:TAKE SHIHONGTAN DISTRICT IN TURPAN-HAMI BASIN AS AN EXAMPLE

In many sandstone type uranium deposits it can be found that uranium is in coexistent relationship with organic matter. The relation may be statistical, spatial or chemical. This paper studies the sandstone type uranium deposit in Shihongtan district, Turpan Hami Basin, and tries to ascertain the role of organic matter in concentrating uranium. The organic matter is of humic type in host sandstone in the studied area, and its original mother material mainly belongs to terrestrial higher plant. The maturity of the organic matter is very low, being in low grade stage of thermal evolution. Correlation analysis and separation experiments show that uranium concentration is colosely related with the organic matter, and the organic matter in uranium ore is mainly in the form of humic acid and humate. Authors suggest that in the mineralizing process of epigenetic sandstone type uranium deposits, humic substances are destroyed and dissolved into ground water in the oxidized sandstone zone. Some uranium could be transported by humic acid complexes, and may be co precipitated with humate at the geochemical barrier (redox front). For this reason the total organic carbon content is often synchronously increased with uranium in the geochemical redox zone in epigenetic sandstone type uranium deposits.